This application relates generally to gas turbine engines and, more particularly, to combustors for gas turbine engines.
At least some known gas turbine engines include annular combustors which facilitate reducing nitrogen oxide emissions during gas turbine engine operation. Because of the heat generated within such combustors during operation, at least some known multiple annular combustors include a plurality of multiple dome assemblies that are radially aligned between the combustor dome plate and the combustion chamber. Each dome assembly includes a heat shield to protect the dome plate from excessive heat generated during engine operation.
At least some known dome assembly heat shields include annular endbodies that extend an axial distance downstream from the heat shield to separate the domes or stages of the combustor to enable primary dilution air to be directed into a pilot stage reaction zone, thus facilitating combustion stability of the pilot stage of combustion at various operating points. However, because the endbodies extend axially towards the combustion chamber, the endbodies are exposed to a high temperature and high acoustic energy environment. Over time, the combination of the high temperatures and high acoustic energy may induce thermal stresses, low cycle fatigue (LCF), and/or high cycle fatigue (HCF) into the heat shield assembly. Continued operation with such stresses may lead to cracking within the heat shield which may shorten the useful life of the combustor.
To facilitate reducing the effects of exposure to the high temperature and high acoustic energy environment, at least some known heat shield assemblies have employed various design changes to facilitate improving heat shield durability by addressing thermal and LCF failures. Such improvements have included for example, increased impingement cooling flow, surface film cooling, material changes, and/or heat shield contour changes to attempt to stiffen the component. However, such improvements did not completely address HCF failures caused by combustor acoustics. More specifically, due to engine-to-engine operating variation, and manufacturing/assembly tolerances, despite the improvements, at least some known heat shield natural frequencies remain within the combustor acoustic operating range, and over time, may still experience failures due to HCF fatigue.
In one aspect, a method for assembling a gas turbine engine multi-domed combustor including an outer liner and an inner liner that define a combustion chamber therebetween is provided. The method comprises coupling a first dome including a heat shield that includes an annular endbody that extends a first distance axially from the heat shield to the combustor outer liner, and coupling a second dome including a heat shield that includes an annular endbody that extends a second distance axially from the heat shield to the first dome, such that the second dome is radially aligned with respect to the first dome, and wherein the second dome second distance is less than the first dome first distance.
In another aspect of the invention, an annular combustor for a gas turbine engine is provided. The combustor includes an outer liner, an inner liner, a first dome, and a second dome. The inner liner is spaced radially inwardly from the outer liner to define a combustion chamber therebetween. The first dome includes an outer end coupled to the outer liner and a heat shield including an annular endbody that extends outwardly a first distance axially from the heat shield towards the combustion chamber. The second dome is spaced radially inwardly from, and radially aligned with respect to the first dome. The second dome includes an outer end coupled to an inner end of the first dome, and a heat shield including at least one annular endbody that extends outwardly a second distance from the second dome heat shield. The second distance is less than the first dome first distance.
In a further aspect, a gas turbine engine including a combustor having a natural combustor acoustic operating range is provided. The combustor includes an outer liner, an inner liner, and a plurality of radially-aligned domes. The outer liner is coupled to the inner liner to define a combustion chamber therebetween. The plurality of domes include at least a first dome and a second dome. The first dome includes a heat shield including an annular endbody that extends a first axial distance from the first dome heat shield. The second dome is radially inward from the first dome and includes a heat shield including an annular endbody extending a second axial distance from the first dome heat shield. The second axial distance is less than the first dome first distance.